Boots having a shell and a foot retention arrangement at the inside of such shell are known, e.g., from U.S. Pat. No. 3,883,964, German Published Application No. 1,801,920 and French Pat. No. 1,587,642.
For example, the ski boots disclosed in French Pat. No. 1,587,642 are provided with one or more straps between the shell and the slipper at the level where the foot joins the ankle, for the purpose of assuring good retention of the foot in the boot. However, this retention is not sufficient, particularly in the upper region, for the purpose of advanced or competitive skiing.
To correct this defect, certain boots (see especially those of U.S. Pat. No. 3,883,964) are provided with a rigid plate located between the shell and an interior slipper precisely at the upper region, and applied against the upper part of the slipper by means of a screw accessible from the outside of the shell. Thus, the retention of the foot in the upper region is improved. However, such a rigid plate system presents certain problems, among them the following:
(1) The direction of forces applied to the rigid plate between the shell and the slipper is contrained in a vertical plane. The result is either poor lateral retention of the foot, or excess vertical pressure to assure the desirable lateral retention.
(2) The screws forcing the rigid plate against the upper portion of the foot are emplaced on the top portion of the boot at the level of the upper in an area of low resistance which must sustain the force of the foot transmitted by the plate, and which is subject to deformation.
(3) The applied stresses are transmitted to the rigid plate via the screws which abut against the plate regions in substantially pin-point manner. The considerable restraints which result create the danger that the plate will be deformed and that painful spots will be formed at the upper part of the foot, more particularly during forward flexion which involves a slight deformation of the rigid shell and momentary high pressure on the screws.
It is an object of the present invention to provide a boot, particularly a ski boot, comprising a foot retention system which permits both good vertical retention and good lateral retention in the upper portion of the foot, while avoiding excess vertical pressure on the foot. Such an arrangement must not transmit stress to the upper boot, so that deformation of this area of least resistance is avoided, and must distribue the pressure necessary for the good retention of the foot to all or part of the frontal area.
To achieve this result, the boot according to the invention comprises a shell and a foot-retention system mounted on the inside of the shell, in the front part of the boot. The latter system in turn comprises a support element, independent of the sole, having a general V-shape, and comprising two side plates extending laterally and upon the top part of the forefoot, corresponding to the shape of the latter at its widest portion, as well as an adjustable means for tightening the support element against the foot, comprising means for displacing the two side plates of the support element and pressing them against the foot while adapting them to the top part of the forefoot, the support element abutting against the rigid shell, preferably laterally.
Thus, the foot is tightened against the internal sole of the boot and is laterally retained by the support element acting in the manner of a gripping "V". The two plates of the support element act in the manner of a gripping "V" upon the top part of the foot while forcing it against the inner sole due to the vertical components of the oblique support forces provided by the said plates of the support element, and retaining it laterally due to the horizontal components of the said oblique support forces.
Since the two plates of the support element have an anatomical shape corresponding to that of the top portion of the foot, and since the two plates are adjustable transversely on the foot, the stresses applied by the support element to the foot are suitably distributed over the entire surface of the top of the forefoot.
Moreover, the arrangement of the foot retention system in the upper region of the forefoot, at least in the widest area essentially corresponding to the metatarsus, permits the avoidance of painful spots at the articulated points. Thus, the arrangement provides heightened comfort without diminishing the technical efficiency of the ski boot.
A further advantage of the foot retaining system according to the present invention resides in the fact that the two plates of the support element act as a gripping "V", thereby performing a simultaneous foot centering function in the shell along its longitudinal axis. This advantage can be utilized for adapting to an ordinary shoe a foot having an abnormal orientation, whether inwardly or outwardly.
Finally, the two plates of the support element are controlled from the exterior of the boot by an adjustable gripping means which permits adjustment of the pressure brought to bear in accordance with the morphology of the skier's foot and the needs of the skier.
Various embodiments of the present invention are possible.
Fore example, according to a first modification, the means for moving the two side plates of the support element can comprise means for simultaneously moving, in opposite directions, the two side plates in a direction transverse with respect to the longitudinal axis of the foot. In this case, the two plates are mounted for transverse movement with respect to the shell, and are independent.
The means for simultaneously moving the two side plates of the support element transversely in opposite directions consist of
(a) a threaded hole, respectively, in each of the two lateral plates of the support element;
(b) a screw transversely mounted on the rigid shell, movably rotatable about its axis and comprising two parts with reverse threading, each screwed into the two threaded holes; and
(c) a control member accessible from the exterior of the rigid shell for turning the screw, the control member preferably also functioning as a stop for the screw.
The means for tranversely moving the two side plates of the support element in opposite directions can also comprise
(d) two pressure elements movably mounted transversely with respect to the rigid shell and respectively abutting an inclined ramp integral with the lateral plate corresponding to the support member; and
(e) means for actuating the two pressure elements from the exterior for transverse translation movement in opposite directions.
According to a second embodiment, the means for transversely moving the two lateral plates of the support element can also comprise means for moving each lateral plate of the support element in a direction substantially orthogonal to the lateral surface corresponding to the upper part of the foot.
The means for moving each lateral plate of the support element, in a direction substantially orthogonal to the corresponding lateral surface of the upper part of the foot, comprise, in the second embodiment,
(a) two pressure elements movably mounted transversely with respect to the rigid shell and respectively abutting an inclined ramp integral with the lateral plate corresponding to the support member; and
(b) means for actuating the two pressure elements from the exterior for transverse translation movement in opposite directions.
The two plates of the support element are preferably connected in a flexible manner with respect to a transverse direction, in such a way as to allow the support element to adapt its shape as closely as possible to the anatomy of the foot.
In both the first and second embodiments, the means for actuating the two pressure elements from the exterior may conveniently comprise
(a) two threaded holes each respectively integral with each of the two pressure elements;
(b) a screw mounted on the rigid shell, movably rotatable about its axis and comprising two parts with reverse threading, each screwed into the corresponding threaded holes; and
(c) an adjustment member accessible from the exterior of the rigid shell for turning the screw, the adjustment member preferably also functioning as a stop for the screw.
In respect to the embodiments just described, the tightening means comprises a screw or worm, but a cable system is also possible.
For example, it is possible to provide a system of crossed cable stretchers attached to the two portions of the support element. These slide on an axis transverse to the longitudinal axis of the foot through the action of cables which bring them into contact with the foot, in order to grip and retain the latter in the shell.
It is also possible to combine the foot retention system according to the invention with flexible means which automatically separate the two parts of the support element, in order to facilitate loosening of the device.
To all these different embodiments, one can add an arrangement for rapid loosening/tightening which makes it possible to discontinue instantly all gripping of the forefoot while yet retaining its original adjustment.